The present invention relates generally to presses for forming belt joints, and more particularly to a press typically used for joining belt ends to form a belt joint.
Belts, and more particularly conveyor belts, are typically manufactured in long strips which are spliced together in one or more locations to form a continuous loop. Due to the stresses imposed on the conveyor belts, it is important that the splice be as high a quality as possible so as to prevent, or at least delay, belt failure at the splice. Over time, a number of methods have been employed to splice belt ends together. The simplest method is the butt splice where the opposing ends of the belt are cut and then bonded together, such as by glue or stapling. Such butt splices are weak. Stronger splices are achieved when there is some sort of overlapping of the two belt ends, such as when the top half of one end and the bottom half of the other end are removed and the complementary portions of the ends are overlapped and bonded together by gluing, etc., and thereafter vulcanized with presses having heated platens. For some applications, it is desirable to form stepped splices having staggered overlapping levels, as disclosed in U.S. Pat. Nos. 5,974,935 and 6,228,200, incorporated herein by reference. In addition, the belt material of the complementary opposing ends may be formed into an interleaved finger arrangement.
A number of belt presses have been designed. Typically, such presses rely on either hydraulic pressure or inflatable bladders to supply the compression force between opposing platens. For instance, U.S. Pat. No. 4,946,541 to Thies et al. discloses a hydraulic press, while U.S. Pat. No. 5,562,796 to Ertel discloses a inflatable bladder press. Hydraulic presses suffer from the disadvantages of requiring extra equipment, such as hydraulic pressure sources, and being unduly complicated. Inflatable bladder presses likewise require additional equipment, such as high pressure air supplies, involve undue complexity, and suffer from the potential for bladder failure. In addition, both types of belt presses require strong, massive reinforcing structures to handle the forces within the presses. Such reinforcing structures are heavy, cumbersome to move, and typically requires extensive assembly on-site.
In light of the above, there remains a need for a simplified belt press which can provide reliable performance for forming belt joints.
The belt press of the present invention generates a compression force between press surfaces facing a belt material, for joining or repairing the belt material, by pulling a vacuum on one side of at least one substantially rigid platen. In this manner, the present invention utlizes a combination of vacuum and atmospheric pressure to provide the majority of the compressive force between platens of a belt press.
Two belt ends are disposed between first and second platens, the first and second platens having respective substantially rigid proximal sides. At least the first platen has a plurality of vacuum ports communicating with its proximal side. A compressive force is generated between the proximal sides of the first and second platens by pulling a vacuum at the vacuum ports associated with the first platen while allowing atmospheric pressure to act against a distal side of the first platen. The vacuum may be applied at both a first group of larger ports disposed generally proximate a perimeter of the proximal surface of the first platen and at a second group of ports, smaller in size, disposed inwardly from the first group. Heat may be applied to the two belt ends via at least one of the first and second platens while generating the compressive force. Evolved gases are vented via the vacuum ports while applying the heat by continuing to pull the vacuum during heating. When the now-joined belt ends have cooled after the application of heat, the compressive force is relieved by ceasing the pulling the vacuum at the vacuum ports associated with the first platen.
The second platen of the belt press may be similar to the first platen. Accordingly, the second platen may have a plurality of vacuum ports communicating with its proximal side and the compressive force may be generated between the proximal sides of the first and second platens by pulling a vacuum at the both the vacuum ports associated with the first platen and the vacuum ports associated with the second platen.